Activation of C-Br Bond of CBr 4 and CBrCl 3 Using 9-Mesityl-10-methylacridinium Perchlorate Photocatalyst.

Herein, we report the activation of the C-Br bond of CBrX 3 (X = Cl, Br) using 9-mesityl-10-methylacridinium perchlorate as a visible-light (12W blue LED, 450-455 nm) photocatalyst for the synthesis of gem -dihaloenones from terminal alkynes. An electron transfer from CBrX 3 to Mes-Acr-MeClO 4 led to the formation of •+ CBrX 3 which subsequently resulted in the intermediate + CX 3 . Next, C-C cross-coupling of + CX 3 with terminal alkynes was the key path to obtain the gem -dihaloenones. Radical trapping experiments with TEMPO, BHT, and Stern-Volmer quenching studies helped to understand that the reaction proceeded via the SET mechanism.